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0 °C

A solution (0.2 M) of ethyl 4-[(tert-butoxycarbonyl)amino]thiophene-2-carboxylate in DCM was cooled to 0° C. and treated with NBS (1.1 eq.) then stirred at 0° C. for 30 min. The mixture was quenched with aqueous Na2S2O3 (saturated solution) and extracted with AcOEt. The organic phase was washed with aqueous Na2S2O3 (saturated solution) and brine then dried and concentrated. The residue was purified by flash chromatography on silica gel (1:12 AcOEt/petroleum ether) to afford the title compound (48%) as a solid. 1H NMR (300 MHz, DMSO-d, 300 K) δ 1.32 (t, J=7.07 Hz, 3H), 1.50 (s, 9H), 4.32 (q, J=7.07 Hz, 2H), 7.81 (s, 1H), 9.13 (bs, 1H); MS (ES+) m/z 350, 352 (M+H)+;

1. customThe mixture was quenched with aqueous Na2S2O3 (saturated solution)
2. extractionextracted with AcOEt
3. washThe organic phase was washed with aqueous Na2S2O3 (saturated solution) and brine
4. customthen dried
5. concentrationconcentrated
6. customThe residue was purified by flash chromatography on silica gel (1:12 AcOEt/petroleum ether)